title: Further characterization of a complement-sensitive mutant of a virulent avian Escherichia coli isolate.
abstract: An attempt was made to characterize the mechanism of complement resistance operating in a virulent avian Escherichia coli isolate. Using flow cytometry to detect antibody to C3, we found that there was significantly more antibody bound to a complement-sensitive mutant of this wild type than to the parent organism, suggesting that more C3 subunits were bound to the wild type. Neither the wild type nor the mutant degraded C3. Further, the mutant was phagocytosed to a significantly greater degree than the wild type by cultured phagocytes in the presence of C5-deficient serum. These data suggest that the wild type is resistant to complement, at least in part, because of its ability to restrict C3 deposition on its surface. Therefore, the decrease in virulence seen in the mutant may be related to its increased sensitivity to complement-mediated bacteriolysis or its enhanced susceptibility to complement-opsonized phagocytosis or both.
authors.affiliation: Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, ND 58105, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Kottom
authors.forename: L K
authors.initials: LK
authors.lastname: Nolan
authors.forename: M
authors.initials: M
authors.lastname: Robinson
authors.forename: J
authors.initials: J
authors.lastname: Brown
authors.forename: T
authors.initials: T
authors.lastname: Gustad
authors.forename: S M
authors.initials: SM
authors.lastname: Horne
authors.forename: C W
authors.initials: CW
authors.lastname: Giddings
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis / Q000276:immunology; D002478:Cells, Cultured; D002645:Chickens; D015169:Colony Count, Microbial; D003176:Complement C3 / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D015932:Complement C3c / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D003182:Complement C5 / Q000172:deficiency / Q000378:metabolism / Q000502:physiology; D004279:DNA, Viral / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods / Q000662:veterinary; D004926:Escherichia coli / Q000235:genetics* / Q000276:immunology* / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D005434:Flow Cytometry / Q000379:methods / Q000662:veterinary; D009154:Mutation; D010586:Phagocytes / Q000473:pathology / Q000502:physiology; D010587:Phagocytosis / Q000502:physiology; D011201:Poultry Diseases / Q000097:blood / Q000382:microbiology / Q000473:pathology*
chemical_list: D000907:Antibodies, Bacterial; D003176:Complement C3; D003182:Complement C5; D004279:DNA, Viral; D015932:Complement C3c